This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my application THE DEVELOPER INTEGRATED WITH HOPPER OF IMAGE FORMING APPARATUS filed with the Korean Industrial Property Office on Oct. 1, 1999 and there duly assigned Serial No.42198/1999.
1. Field of the Invention
The present invention relates, in general, to a developing unit for an image forming apparatus. More particularly, it relates to a hopper-integrated developing unit for an image forming apparatus.
2. Description of the Related Art
A conventional developing unit, to which a developing roller, and a photosensitive drum, a hopper containing toner are mounted, is installed in a laser printer or copying machine.
Such a developing unit may be classified into a recycling type unit or a non-recycling type unit. The recycling type developing unit can be reused with an old hopper replaced with a new hopper, because its hopper containing toner may be removed. On the other hand, a non-recycling type developing unit must have its entire developing unit replaced with a new one after the consumption of toner because the hopper is integrated with the remaining portions of the developing unit. Therefore, when toner is consumed the conventional hopper-integrated developing unit must be replaced with a new developing unit.
Nevertheless, some reproduction companies provide at a low price reproduced developing units that are filled with toner while their old photosensitive drums, developing rollers and supply rollers are not replaced with new parts. These inferior reproduced developing units not only do harm to the image of a genuine developing unit manufacture, but also cause inconvenience to the users of the developing units because of frequent breakdowns.
To solve this problem, proposals have been made for mounting screws to be rotatable for assembly and to be non-rotatable for disassembly so as to prevent a supply roller, a developing roller and a photosensitive drum from being removed from a case, or side plates are assembled with the case using an ultrasonic or thermal fusion bonding process. However, such proposals create a problem. When a breakdown occurs just after the assembly of the developing unit is completed, the developing unit must be discarded because the side plates cannot be removed from the case.
Accordingly, an object of the present invention is to provide a hopper-integrated type developing unit for an image forming apparatus, which is capable of preventing the developing unit from being removed from a case for the filling of toner.
Another object of the present invention is to provide a hopper-integrated type developing unit for an image forming apparatus, in which the developing unit can be removed from a case using a jig without damaging when breakdown occurs just after the developing unit is assembled with the case.
In order to accomplish the above object, the present invention provides a hopper-integrated type developing unit for an image forming apparatus, comprising: a case consisting of a body and side plates; a supply roller, a developing roller and a photosensitive roller accommodated in the case; a supply roller retaining shaft around which the supply roller is fixedly fitted and which is rotatably held by the side plates of the case at its both ends; a developing roller retaining shaft around which the developing roller is fixedly fitted and which is rotatably held by the side plates of the case at its both ends; two photosensitive drum retaining shafts respectively fixed to side plates at its inner ends and respectively inserted into an interior of the photosensitive drum at its outer ends; driving gears being respectively fitted around the retaining shafts and transmitting rotating force to the supply roller, the developing roller and the photosensitive drum while being rotated connectively; and removal restricting means which allows the supply roller retaining shaft and the developing roller retaining shaft to be combined with and removed from the side plates of the case only at one engagement state of the driving gears.
Preferably, the removal restricting means may comprise removal restricting projections respectively formed on one side end portions of the supply roller retaining shaft and the developing roller retaining shaft, and accommodating means for receiving one side ends of the supply roller retaining shaft and the developing roller retaining shaft.
Preferably, the accommodating means may be engaging bosses, which are formed on one of the side plates of the case and respectively have openings having shapes respectively corresponding to the sectional shapes of the supply roller retaining shaft and the developing roller retaining shaft at positions where the removal restricting projections are formed.